1. Field of the Invention
The present invention relates to an apparatus for driving a lens for use with a disk player for recording information to a disk or reading recorded information therefrom.
2. The Description of Related Art
An apparatus for driving a lens is well-known, including a pickup apparatus for reading information of an optical disk. The lens drive apparatus is for properly correcting a relative position between a track on a disk and an objective lens by driving the objective lens in a focus direction and a tracking direction. The apparatus is driven based on a focus error signal and a tracking error signal.
FIG. 1 shows one example of a conventional apparatus for driving a lens. Numeral 310 designates an actuator base of a magnetic material, and has a suspension base 308 fixed vertically. A lens holder 302 is provided with an objective lens 301, a focusing coil 303, and a tracking coil 304 to form a movable member. The lens holder 302 is coupled to the suspension base 308 through four suspension wires 305 extending in a tangential direction. Therefore, the lens holder 302 is floatingly supported in a cantilever manner, and movable in a focus direction and the tracking direction. It should be noted that the four suspension wires 305 also serve as power feed lines for a driving current to the focusing co 303 and the tracking coil 304.
The actuator base 310 is provided with four projecting pieces to which magnets 311 are fixed, thereby forming a magnetic circuit. The focusing coil 303 and the tracking coil 304 are arranged in a magnetic gap of the magnetic circuit, and has a magnetic flux applied thereto.
In the above-described constitution, when a driving current is supplied to the focusing and tracking coils 303 and 304 in response to focus and tracking error signals, a driving force (electromagnetic force) directed in the focus direction and the tracking direction is generated from these coils. Then, the lens holder 2 is driven, and a servo control for moving the objective lens 1 to a proper position can be performed.
In the lens drive apparatus, an approach is required to avoid a swing phenomenon in which the lens holder 302 is inclined when the lens holder 30 is driven in the tracking direction. That is, as shown in FIG. 2, when the center of gravity G of the movable member is not on an action line F of a tracking driving force, a drawback occurs that the lens holder 302 may swing by a moment force. Therefore, as shown in FIG. 3, The adjustment to move the center of gravity G on the action line F is performed by fixing a counter weight 307 having a desired weight to the lens holder 302.
Furthermore, since the objective lens 301 is fixed to an upper surface of the lens holder 302, the center of gravity G of the movable member is deviated from the center of gravity of the lens holder 302. Therefore, the counter weight 307 is fixed to a lower surface of the lens holder 302, thereby forming a weight balance with respect to the objective lens 1.
However, the above approach increases the weight of the movable member by the weight of the counter weight, since the counter weight 307 is fixed to the lens holder 302. The above problems may causes the degradation of the sensitivity of an actuator, and makes an instantaneous position correction for the objective lens 301 more difficult.
An object of the invention is to solve the above problems, and to provide an apparatus for driving a lens without a swing phenomenon and the degradation of the sensitivity of an actuator.
In order to solve the above-described problem, an aspect of the invention is characterized by an apparatus for driving an objective lens for use with a disk player, comprising a movable lens holder provided with driving coils and the objective lens, and a magnetic flux producing assembly for producing magnetic flux to the driving coils to move the objective lens in tracking and focusing directions of a disk, wherein the driving coils comprise at least one set of two tracking coils, each of the tracking coils having a flat coil face, wherein the magnetic flux producing assembly produces a first magnetic flux orthogonal to a coil face of the tracking coil in a first area including a first part of the tracking coil, and a second magnetic flux in a second area including a second part of the tracking coil other than the first part, said second magnetic flux having a direction opposite to that of the first magnetic flux, and wherein at least a portion of a boundary surface between the first and second areas is inclined from a focusing direction of the objective lens.
Another aspect of the present invention is characterized in that an apparatus for driving an objective lens for use with a disk player, comprising a movable lens holder provided with driving coils and the objective lens, and a magnetic flux producing assembly for producing magnetic flux to the driving coils to move the objective lens in tracking and focusing directions, wherein the driving coils comprise at least one set of two tracking coils, each of the tracking coils having a flat coil face, wherein the magnetic flux producing assembly comprises an N pole face and an S pole face in a plane facing to the tracking coil, and at least a part of a boundary surface of the N and the S pole is inclined toward a focusing direction of the objective lens.
A further aspect of the present invention is characterized in that an apparatus for driving an objective lens for use with a disk player, comprising a movable lens holder provided with driving coils and the objective lens, and a magnetic flux producing assembly for producing magnetic flux to the driving coils to move the objective lens in tracking and focusing directions, wherein the driving coils comprise at least one set of two tracking coils, each of the tracking coils having a flat coil face perpendicular to a reading direction of the disk player, wherein the magnetic producing means comprises first and second pole faces placed along the reading direction to form a magnetic gap between the first and second pole faces, in which a part of the tracking coil is placed, and at least a portion of a contour surface between the first and second pole faces is inclined toward a focusing direction of the objective lens.
A still further aspect of the present invention is characterized in that an apparatus for driving an objective lens for use with a disk player, comprising a movable lens holder provided with driving coils and the objective lens, and a magnetic flux producing assembly for producing magnetic flux to the driving coils to move the objective lens in tracking and focusing directions, wherein the driving coils comprise at least one set of two tracking coils, each of the tracking coils having a flat coil face, wherein the magnetic flux producing assembly produces a first magnetic flux orthogonal to a coil face of the tracking coil in a first area including a first part of the tracking coil, a second area including a second part of the tracking coil other than the first part lacking magnetic flux, and wherein at least a portion of a boundary surface between the first and second areas is inclined toward a focusing direction of the objective lens.
As described above, according to the apparatus of the invention, since the swing movement of the movable member can be suppressed without using a counter weight, the weight of he movable member can be reduced. There can be provided a lens drive apparatus having fine sensitivity of an actuator and capable of avoiding the swing movement of the movable member.